The present invention relates to a magnetic head slider, and in particular to a magnetic head slider with a high recording density and a high degree of reliability.
Further, the present invention also relates to a magnetic disc unit incorporating the above-mentioned magnetic head slider.
A magnetic head slider flies on a magnetic disc on rotation by air-bearing so as to allow a magnetic head carried thereon to record or reproduce data onto and from a recording medium. For example, U.S. Pat. No. 5,777,825 discloses a slider which has a leading edge side step surface and a trailing edge sidestep surface, two side rails connected to the leading edge side step surface and extended toward the trailing edge side step surface, pads provided respectively on the leading edge side step surface and the trailing edge side step surface and defining a vacuum pocket between the side rails, and which is adapted to reduce the tendency of high dependency upon a flying height thereof. This slider is configured so as to reduce the tendency of high dependency upon a flying height thereof.
It is noted that a flying height at the beginning of contact with the media surface (which will be hereinbelow referred to as “contact start flying height”) hto is defined as to the flying of the slider. There are presented minute wavy unevenness and minute protrusions caused by surface-roughness on the recording medium surface of a disc, and the slider comes into contact with tip ends of those of the minute protrusions having a maximum height as the flying height of the slider flying on the surface of the disc is decreased. This maximum height of the tip ends of the protrusions, measured from an ideal plane of the disc, is called as the above-mentioned contact start flying height hto. This contact start flying height is sometime distinguished from a flying height measured from an ideal surface of a disc having no surface roughness.
The above-mentioned slider induces a vacuum in the vacuum pocket so as to reduce variation in the flying height due to variation in atmospheric pressure around the slider. Comparing with a slider without using a vacuum, since the slider flies on the disc in such a condition that a difference in flying height between the leading edge and the trailing edge thereof is small or the pitch angle thereof is small, the surface of the slider which makes contact with a flat medium surface of the disc having a low contact start flying height hto or a low maximum height of the tip ends of minute protrusions becomes larger, and accordingly, there would be caused a problem of increasing vibration due to the contact. Further, if wavy unevenness such as run-out, having a long wavelength is present on the medium surface of a disc, variation in pressure is caused between the floating surface of the slider and the medium surface due to the wavy unevenness, and accordingly, the flying height varies. Since the slider using a vacuum has a small available pitch angle in comparison with a slider without using a vacuum, the area of the air bearing surface upon which variation in pressure is exerted, becomes larger, and as a result, variation in the flying height caused by run-out becomes larger.